Average global warming could hit the crucial threshold of 1.5°C above pre-industrial levels in less than 10 years, marine climatologists are reporting, if short-term warming from the Pacific equivalent to El Niño pushes the atmosphere into overdrive.
The Interdecadal Pacific Oscillation (IPO) moves back and forth between relatively warm and relatively cool states, just as El Niño and La Niña describe hot and cold temperature phases along an elongated triangle of equatorial ocean off the west coast of South America, explained Ben Henley of the University of Melbourne. “The IPO is like the long-term version of El Niño—it’s like El Niño’s uncle,” added Henley, lead author of a recent paper in the journal Geophysical Research Letters.
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In its cool, negative phase, the Oscillation absorbs heat from the air. In its warm, positive one, it releases heat back out to the atmosphere—driving weather changes around the globe. But unlike the two- to seven-year Niño/Niña cycle, the Pacific Oscillation occurs over decades and involves a much vaster expanse of ocean—hence much greater amounts of heat.
The IPO was negative from 2000 to 2014, when scientists believe it absorbed much of the planet’s additional heat, providing a “temporary buffer” against the surface of the Earth feeling hotter over that period (and contributing to a popular fake news narrative that warming had paused or gone into reverse).
However, that has changed. Since 2014, the Pacific Oscillation has appeared to be swinging back into a positive phase that would release enormous amounts of stored-up heat back to the atmosphere, Henley and co-author Andrew King warn.
“The negative phase might have lulled us into a false sense of security—the planet appears temporarily to not be warming as fast,” Henley told Australia’s Fairfax Media. “A turnaround of the IPO to its positive phase could initiate a period of accelerated warming. This would likely lead to the Paris target of 1.5°C being surpassed within the next decade.”
Small island states in the Pacific have said that target is both necessary to their survival, and achievable. But the new research lends alarming reinforcement to observations in early 2016 that the global temperature had reached an average that was already 1.46ºC above pre-industrial levels.
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